Jamaica, Mexico to feel Dean's wrath

A dangerous Category 4 Hurricane Dean will crash onto Jamaica's southern beaches by 1 p.m. Central time Sunday, as it continues to speed west-northwest at 18 mph towards Mexico's Yucatan Peninsula and on to a final landfall on the Mexico coastline south of the Texas border.

At 4 p.m., Dean's eye was about 455 miles east-southeast of Kingston, Jamaica. The storm had maximum sustained winds of 150 mph, and forecasters warned that some parts of the island might see 20 inches of rain.

The National Weather Service forecast cone of error has continued to narrow southward, as a variety of computer models continues to agree on the ultimate Mexico or southernmost Texas landfall late Wednesday or early Thursday.

The National Hurricane Center forecast calls for Dean to strengthen to a Category 5 before losing strength as it cuts across the Yucatan Peninsula. But it will return to at least Category 3 strength as it crosses the Bay of Campeche in the Gulf of Mexico.

Senior forecaster Lixion Avila, in his 4 p.m. Central time hurricane discussion message said a reconnaissance aircraft investigating the storm found a double eyewall, a possible indicator that the storm is in an eyewall replacement cycle that will cause its intensity to fluctuate over the next few hours.

Dean continues to grow in size, with hurricane force winds extending up to 70 miles from its center. Tropical storm-force winds extend out 230 miles, and already are affecting Punta Cana in the Dominican Republic.

Jamaica's Meteorological Service warned that the island will begin experiencing tropical storm-force winds overnight, and could see 10-foot storm surge accompanied by huge, battering waves. The heavy rains alco could cause flash floods and landslides, it warned.
So what caused Dean to rapidly increase in strength and then stay strong over the past few days? National Hurricane Center forecasters point to a growth-enabling combination of ocean and atmospheric features, including warm sea surface temperatures and light or non-existent upper level wind shear.

Ocean temperatures, however, may be the biggest factor.

Beginning at the southern end of the Caribbean, sea surface temperatures are about 84 degrees Fahrenheit, increasing to 88 degrees or warmer to the north surrounding the Yucatan Peninsula.

Here's a map of today's sea surface temperatures made available through the University of Miami's Rosenstiel School:http://isotherm.rsmas.miami.edu/heat/data/tsst_latest.gif
The data comes from the NASA/National Space Development Agency of Japan Tropical Rainfall Measuring Mission, or TRMM, satellite's Microwave Imager.

Sea temperatures in the Caribbean are between ½ degree and 1 ½ degrees Celsius warmer than the average temperatures for the period between 1970 and 2000, according to the most recent analysis by NOAA's Global Climate and Weather Modeling Branch: